Removed deprecated dependencies that are now integrated

[Lew-Goldstein]

dash_bootstrap_components, dash_html_components, and dash.dependencies are now integrated into core dash, so modified Import statements to reflect this change in the demo app.

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• The project was correctly built with npm run build.
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• All changes were documented in CHANGELOG.md.
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Reference Issues

Closes #[issue number]

Other comments

[jourdain]

Rather than commenting then, I would remove the lines unless you want to add a comment stating this is for dash<=version

[ndrezn]

Is it worth writing an import that supports various versions, like:

import dash
if hasattr(dash, "html"):
    html = dash.html
else:
    import dash_html_components as html

to catch dcc/Input/Output/... if users are running this on Dash < 2.0.0, or should we expect only >2.0 to be using these examples?

[alexcjohnson]

For demos/examples, at this point I think assuming Dash 2.x is fine. If these imports were inside the package though we'd definitely still want 1.x fallbacks.

[alexcjohnson]

Nonblocking, but some styleguides/linters complain that this is a duplicate import. This is why most of our examples now explicitly import everything you're going to use - in this case that would add Dash and no_update which then lose the dash. prefix below - so you can drop the plain import dash.